It is usual to monitor communications transmission technology facilities in view of their operating condition and signal service disruptions. Such devices for disruption signalling are known, for example, from the Siemens Zeitschrift 48 (1979), supplement "Nachrichten-Ubertragungstechnik", pp. 334 and 335. For example, the outage of supply voltages which serve for supplying communications technology apparatus is thereby indicated.
For example, for communications transmission technology power supply devices, the normal condition and the malfunction condition can be signalled since, as a normal status signal, a grounded potential is connected through in opposition to a feed voltage. Also, in the malfunction case, this signal is disconnected and a grounded potential is supplied instead in opposition to the same feed voltage as the malfunction status signal. The malfunction status signals can thus be preferably displayed with the assistance of a display element. The operating voltage for the signalling circuit itself is preferably independent of the feed voltage of the signal evaluation.
When monitoring circuits having an open collector output are employed for the devices to be monitored, then an OR operation can be achieved in a simple manner by connecting the outputs for the error messages in parallel. A signalling circuit is then required for controlling the signalling device, this signalling circuit supplying grounded potential at the corresponding output dependent on the output signals of the monitoring circuits. A malfunction status can then be optically displayed under given conditions.
The signalling circuit can be dimensioned for a specific operating voltage and can be adapted to the operating voltage respectively available. It is adapted with dropping resistors of various sizes in rough steps via internal bridges or by modifying the rack wiring. This involves additional expense, however. When a voltage regulator is provided for the operating voltage, then an undesirably high dissipated power already results in the normal status.